Collaborative Research: Deciphering Induced-Charge Electrokinetics: Multiscale Simulations and Nanoscale Flow Characterization

合作研究：解读感应电荷电动学：多尺度模拟和纳米级流动表征

• 批准号: 1336224
• 负责人: Rui Qiao
• 金额: $ 16.26万
• 依托单位: Clemson University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2014-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1336224&HistoricalAwards=false
• 关键词: Collaborative; Research; Deciphering; Induced; Charge

Qiao/Wang1336224/1336004Induced-charge electrokinetics (IC-EK) is a class of transport phenomena originating from the migration of induced space charges in electrolytes driven by electrical fields. Because of its distinct advantages over the classical EK in fluid/particle manipulation, IC-EK is expected to bring significant breakthroughs to microfluidic technologies. A fundamental understanding of IC-EK is, however, still lacking: although some experimental trends can be explained, theories often overpredict experimental measurement by 10-100 folds, and some observations cannot be explained even qualitatively. This suggests that some important physics are missing from the existing theories. Identifying and elucidating such physics is important for advancing the basic understanding of IC-EK and for exploring IC-EK's potential in microfluidic technologies to the fullest extent. Intellectual Merit :The objective of this collaborative effort is to investigate IC-EK using alternating current electroosmotic flow (AC-EOF), a representative member of IC-EK, as a model problem. The central hypothesis is that the discrepancy between experiments and existing theories is caused by a lack of accurate account of the Stern layer, rheology of interfacial fluids, non-equilibrium electrical double layers (EDLs), and their coupling with fluid flow in existing theories. Driven by this hypothesis, two specific objectives are planned: 1) to develop a multiscale simulation tool that accurately accounts for the Stern layer and the rheology of interfacial fluids, and explicitly resolves the ion/fluid dynamics in non-equilibrium EDLs and bulk electrolytes; 2) to elucidate the experimental anomalies of AC-EOF by integrating multiscale modeling with nanoscale flow characterization and to explore new design of AC-EOF-based device using the insights gained in this work. The planned flow measurement will resolve flow within the nanoscopic non-equilibrium EDLs and the dynamics of vortices near electrodes. Together, these studies will enable the underlying physics of the experimental anomalies of AC-EOF to be delineated with unprecedented accuracy. The research is potentially transformative. First, the insights gained here will lay foundation for the rational design of AC-EOF devices to overcome their limitations. Second, by elucidating the impact of the rheology of interfacial fluids on EOF and the role of non-equilibrium EDLs in AC-EOF, this study will significantly advance EK theory. In particular, quantitatively confirming the importance of non-equilibrium EDLs in AC-EOF can potentially lead to a paradigm shift in how the entire class of IC-EK transport is understood and controlled.Broader Impacts :A series of activities are planned to encourage and prepare undergraduate students to pursue careers in computational science and engineering. Students participating in this interdisciplinary project will be exposed to diverse fields such as computational electrohydrodynamics and interfacial sciences. Various resources, e.g., the minority recruitment/retention programs at the PIs' institutions, will be utilized to recruit students from under-represented groups to participate in this project. These activities will benefit from the PIs' experience with these programs. Research results will be developed into modules for the micro/nanofluidics courses taught by the PIs. Research results will also be developed into videos and posters for use in K-12 outreach activities and for submission to the gallery of fluid motion/images hosted by Efluids.com.

Qiao/Wang1336224/1336004诱导的电动电动器（IC-EK）是一类传输现象，源自电场驱动的电解质中诱导的空间电荷的迁移。由于其在流体/颗粒操作中具有与经典EK的不同优势，因此IC-EK有望为微流体技术带来重大突破。然而，对IC-EK的基本理解仍然缺乏：尽管可以解释一些实验趋势，但理论通常过度预测实验测量值10-100倍，甚至无法定性地解释一些观察结果。这表明现有理论缺少一些重要的物理。识别和阐明这种物理学对于促进对IC-EK的基本理解以及在最大程度上探索IC-EK在微流体技​​术中的潜力很重要。智力优点：这项协作工作的目的是使用IC-EK的代表成员使用当前的电流流动流（AC-EOF）来调查IC-EK，作为模型问题。中心假设是，实验和现有理论之间的差异是由于缺乏对船尾层，界面流体的流变性，非平衡电气双层（EDLS）的流变以及它们与现有理论中流体流的耦合所致。在这一假设的推动下，计划了两个特定的目标：1）开发一种多尺度模拟工具，该工具准确地说明了肠层和界面流体的流变，并明确解析了非平衡EDL和散装电解质的离子/流体动力学； 2）通过将多尺度建模与纳米级流程进行整合，并使用本工作中获得的见解来探索基于AC-EOF的设备的新设计，以阐明AC-EOF的实验异常。 计划的流量测量将解决纳米非平衡EDL中的流量和电极附近涡流的动力学。总之，这些研究将使AC-EOF实验异常的潜在物理学能够以前所未有的精度描绘。这项研究具有潜在的变革性。首先，这里获得的见解将为AC-EOF设备的合理设计奠定基础，以克服其局限性。其次，通过阐明界面流体对EOF的流变学的影响以及非平衡EDL在AC-EOF中的作用，这项研究将显着提高EK理论。特别地，定量证实非平衡EDL在AC-EOF中的重要性可能会导致整个IC-EK运输类别的理解和控制方式的范式转移。Boader的影响：一系列活动计划鼓励和准备本科生在计算科学和工程学中从事职业生涯。参加这个跨学科项目的学生将接触到各种领域，例如计算电水动力学和界面科学。各种资源，例如，PIS机构的少数民族招聘/保留计划将用于招募来自代表性不足的团体的学生参加该项目。这些活动将受益于PIS对这些计划的经验。研究结果将发展为PIS教授的微/纳米流体课程的模块。研究结果还将发展到视频和海报中，以用于K-12外展活动，并将其提交给Efluids.com托管的流体运动/图像画廊。